The present invention relates to piezoelectric transducers for generating ultrasonic oscillations for disintegrating bladder, urethra and kidney stones, of the kind which comprise two piezoelectric discs clamped between two metal elements and of which the metal element at the distal side has screwed into it an end fitting to which is connected a wire for transmitting the ultrasonic oscillations, passing through a plastics material sheath connected to the end fitting and having a basket-like loop structure projecting distally out of the sheath.
In the case of the aforesaid known piezoelectric transducers, the plastics material sheath connected to the end fitting is traversed by a single wire only, acting as a transmission element for the ultrasonic oscillation, as described in German Patent Specification No. DE-PS 20 20 345, for example. It is known moreover that a wire may be connected at the distal end projecting out of the sheath to a basket-like loop structure (Dormia loop structure), which serves the purpose of receiving a stone which is to be removed. The combination in accordance with the prior art referred to, in conjunction with an ultrasonic transducer, is not completely successful because this system tends to fracture easily on the one hand due to inadequate strength, and on the other hand because the efficiency of the ultrasonic oscillations for destroying the stones is very low, since the transverse oscillations required to this end cannot be transmitted.
It is an object of the invention to provide a transducer in which the transmission element extends from the end fitting to the loop structure in morphologically stable form and to obtain greater durability by reducing the risk of fracture, as well as a high efficiency during transmission of longitudinal and transverse oscillations to the stone.